On March 15, 1858, five members of the New York City Police Department rowed out into New York Harbor to combat piracy aboard merchant ships lying at anchor. The NYPD Harbor Unit has existed ever since, protecting life and property. With hundreds of miles of inland waterways to cover, the unit operates over 36 boats from four bases. For underwater work, the department used to contract with private diving companies when weapons or other evidence had to be recovered from the bottom of New York's many rivers and waterways. In the early 1970s, however, the Harbor Unit formed a specialized scuba team that today numbers around 30 officers. Unlike many police dive units, whose members dive only part-time, NYPD divers are assigned to the unit full-time. (The exception are some scuba-trained officers in regular patrol units who are detailed to the team temporarily during the busy summer months.) In addition to the normal duties of evidence recovery, the Scuba Team's mission has expanded since 9/11 to include a counter-terrorism role. For air-sea rescue work, the Harbor Unit keeps two divers assigned to the Aviation Unit 24 hours a day, seven days per week, all year round. These divers will work with their counterparts in the FDNY, who arrive at incidents by fireboat or rescue company.